Field of the Invention
The present invention relates to a spring mechanism that includes a transducer that has an elastic deformation part with a film shape, which elastically extends and contracts in a direction along a face, depending on input energy, and to a linear motion displacement mechanism which has the spring mechanism.
Description of the Related Art
Conventionally, a mechanism is known that is described, for instance, in FIG. 6 to FIG. 8 of Japanese Patent Laid-Open No. 2009-41463, as a mechanism corresponding to the spring mechanism which includes the transducer that has the elastic deformation part with the film shape, which elastically extends and contracts in the direction along the face, depending on.
The spring mechanism described in the above described Japanese Patent Laid-Open No. 2009-41463 includes: an electrostrictive element as the transducer, which has the elastic deformation part that includes an elastic film made from a dielectric elastomer and electrodes for applying voltage in the thickness direction; and also a housing which accommodates the electrostrictive element therein. The edge part of the elastic deformation part of the electrostrictive element is supported by a side wall of the housing.
Furthermore, in the mechanism described in FIG. 6 and FIG. 7 of Japanese Patent Laid-Open No. 2009-41463, a rod which is provided so as to extend to one side out of both sides in a thickness direction of the elastic deformation part, from the central part of the elastic deformation part of the electrostrictive element, penetrates the through hole formed in the housing.
In addition, in a mechanism described in FIG. 8 of Japanese Patent Laid-Open No. 2009-41463, a rod which is provided so as to extend to both sides in the thickness direction of the elastic deformation part, from the central part of the elastic deformation part of the electrostrictive element, penetrates the through hole formed in the housing.
Any of the mechanisms is structured so that the central part of the elastic deformation part is displaced in the central axis direction (shaft center direction of rod) of the elastic deformation part, by the extension and contraction in a direction along the face of the elastic deformation part, and so that the rod moves (linearly moves) in synchronization with the displacement.
Accordingly, any of the mechanisms is structured so as to be capable of transmitting an elastic force which has been generated by the extension and contraction of the elastic deformation part of the electrostrictive element, to the outside through the rod. In addition, the mechanism can also change the rigidity of the elastic deformation part by changing voltage to be applied to the elastic deformation part (consequently by changing input energy).
In the transducer provided in the spring mechanism as described in the above described Japanese Patent Laid-Open No. 2009-41463, the central part of the elastic deformation part can be displaced with a comparatively large stroke, by elastic deformation corresponding to the extension and contraction in the direction along the face of the elastic deformation part. Consequently, a stress tends to easily concentrate on the vicinity of the central part of the elastic deformation part of the transducer, during the elastic deformation.
Because of this, particularly if the elastic deformation of the elastic deformation part of the transducer becomes an imbalanced deformation (elastic deformation having low symmetry of elastic deformation shape), during the elastic deformation in which the displacement in the central part of the elastic deformation part becomes comparatively large, a damage such as a crack of the elastic deformation part due to local stress concentration tends to easily occur.
Here, in the spring mechanism having the structure described in FIG. 6 and FIG. 7 of the above described Japanese Patent Laid-Open No. 2009-41463, the rod which is provided so as to extend from the central part of the elastic deformation part of the electrostrictive element (transducer) penetrates the through hole of the housing on one side in the thickness direction (central axis direction) of the elastic deformation part. Because of this, if a length of the through hole is sufficiently increased, it is possible to displace the central part of the elastic deformation part so that the elastic deformation of the elastic deformation part does not become the imbalanced deformation as much as possible (so that symmetry of elastic deformation shape is kept).
However, in this case, it is necessary to sufficiently increase the length of the above described through hole, and accordingly it is necessary to increase the thickness of the housing which has the through hole formed therein. Consequently, the size of the spring mechanism results in being enlarged.
In addition, in the spring mechanism having the structure described in FIG. 8 of the above described Japanese Patent Laid-Open No. 2009-41463, the rod which is provided so as to extend from the central part of the elastic deformation part of the electrostrictive element (transducer) penetrates the through hole of the housing, on both sides in the thickness direction (central axis direction) of the elastic deformation part. In this case, the through holes exist in both of the sides in the thickness direction of the elastic deformation part, and accordingly it is possible to displace the central part of the elastic deformation part so that the elastic deformation of the elastic deformation part does not become the imbalanced deformation as much as possible (so that symmetry of elastic deformation shape is kept), even when the length of the through hole is comparatively short.
However, in this case, the rod results in appearing from and disappearing into the housing on both sides (both sides in the thickness direction of the elastic deformation part) of the housing, and accordingly a space necessary for the arrangement of the spring mechanism results in being large.